RAID arrays may be configured in ways that provide redundancy and error recovery without any loss of data. RAID arrays may also be configured to increase read and write performance by allowing data to be read or written simultaneously to multiple disk drives. RAID arrays may also be configured to allow “hot-swapping” which allows a failed disk to be replaced without interrupting the storage services of the array. The 1987 publication by David A. Patterson, et al., from the University of California at Berkeley titled “A Case for Redundant Arrays of Inexpensive Disks (RAID)” discusses the fundamental concepts and levels of RAID technology.
RAID storage systems typically utilize a controller that shields the user or host system from the details of managing the storage array. The controller makes the storage array appear as one or more disk drives (or volumes). This is accomplished in spite of the fact that the data (or redundant data) for a particular volume may be spread across multiple disk drives.